1. Field of the Invention
The present invention relates to a laser type engine ignition device for igniting an air-fuel mixture supplied into a combustion chamber of the engine by a laser.
2. Description of the Related Art
Usually, the ignition condition of the combustion chamber changes very much according to engine operating condition, pressure, temperature, engine rotation speed, engine load, etc. Although it is necessary to properly control laser oscillation in order to secure complete ignition and a sufficient combustion speed, a conventional laser type ignition device, such as disclosed in JP-A-10-196471, can not sufficiently control laser oscillation, so that a complete ignition or a combustion speed can not be provided.
Generally, when the energy density of the laser beam at a condensing position becomes a threshold value, a breakdown takes place resulting in generation of plasma, which causes fuel combustion.
As a means to increase laser peak power, there is a switching technology to generate short pulses. In particular, a solid-state laser oscillator that uses a saturable absorber as a Q-switching element to be stimulated by a laser diode is noteworthy. Such a solid-state laser oscillator is disclosed in JP-A-2003-198019. However, the output laser power of such a solid-state laser oscillator is still insufficient for stable engine operation.